https://www.youtube.com/watch?v=GddZ3pXiDys&list=PLC5E3906433F5A165&index=28†This video of Cassandra summit 2012 has mentioned the use of 256 tokens by default (though it's no longer in the conf/cassandra.yaml). I remember that more tokens could lead to more disk seeks or something. I think 256 is an empirical number based on tests of the speaker.†

Here are two more related articles that you want to read.†
http://www.acunu.com/2/post/2012/07/virtual-nodes-strategies.html
http://www.acunu.com/2/post/2012/10/improving-cassandras-uptime-with-virtual-nodes.html


On Sat, Jan 5, 2013 at 12:18 AM, Michael Kjellman <mkjellman@barracuda.com> wrote:
http://www.mail-archive.com/user@cassandra.apache.org/msg26528.html

From: Alain RODRIGUEZ <arodrime@gmail.com>
Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org>
Date: Friday, January 4, 2013 6:00 AM
To: "user@cassandra.apache.org" <user@cassandra.apache.org>
Subject: num_tokens - virtual nodes

Hi,

I just discover the vnodes new feature described here:†http://www.datastax.com/dev/blog/virtual-nodes-in-cassandra-1-2

In the post above, Brandon says "If youíd like to upgrade an installation to virtual nodes, thatís possible too, but Iíll save that for a later post". Does this post now exist somewhere ?

From the cassandra.yaml:

# If you already have a cluster with 1 token per node, and wish to migrate to
# multiple tokens per node, see http://wiki.apache.org/cassandra/Operations
# num_tokens: 256

I see no reference to vnodes or num_tokens on this wiki.

So, how to switch from "physical" nodes to vnodes ?

This is useful only if your number of nodes is greater than the RF, right ?

Why 256 token by default ? Where this value come from ?

Is there more advantage / disadvantage of using vnodes that improving the internodes data streaming by increasing the number of data sources ?

Alain

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